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Dermatophytosis |
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Infections of the keratinized epithelium
- Microsporum
- Trichophyton
- Epidermophyton
Historical
- Greeks - circular lesions (herpes)
- Romans - insects
- English - ringworm
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Distribution and Ecology |
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Distribution
- Worldwide - some species have restricted distribution
All 3 genera are keratinophilic
- Related physiology, antigenicity, disease potential
Natural reservoir
- Geophilic - (soil saprophytes - M. gypseum)
- Zoophilic - (animals - M. canis)
- Anthropophilic - (humans - T. mentagrophytes)
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Animal Disease |
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- Zoonotic infection - Beware!
Cats - M. canis
- Lesions may not be obvious
- Very contagious
Dogs- M. canis
- Lesions vary from inapparent to severe
- Cattle - T. verrucosum
- Pigs - M. nanum
- Horses - T. equinum and others
- Poultry - M. gallinae
- Primates - T. simii, T. mentagrophytes
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Pathogenesis of Dermatophytosis |
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- Incubation - enter hair follicles
Spread
- Grow downward along hair shafts
- Invade to zone of keratinization (Adamson’s fringe)
- Arthrospores form as hairshaft grows upward
- Refractory period - hairs break, hyphae lost
- involution - hairs return to normal
- Reinfection or recrudescence
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Classification - human ringworm |
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- Tinea capitis
- Ectothrix
- Endothrix
- Tinea corporis - smooth skin
- Tinea cruris - "jock itch"
- Onychomycosis - infection of nails
- Tinea pedis - "athletes foot"
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Host response |
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- Lesions can be very inflammaotry
- More severe inflammation, more likely that organism will be cleared
- Lots of inflammatory cells (PMNs)
- Exudate - lactoferrin, etc.
- Evidence of both humoral and cellular immune response
- "Ids"
- Use of vaccines?
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Identification and isolation |
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- Gross observation - broken hairs,
- Woods lamp - fluorescent hyphae
Direct microscopic observation
- Hairs, skin scrapings
- Clear with chlorphenalac or KOH
DTM medium - selective/differential
- Antibiotics to inhibit bacteria and saprophytic fungi
- Phenol red to detect pH changes
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Treatment |
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Systemic drug treatment
- Griseofulvin
- Itraconazole
Topical treatment
- Clipping
- Dipping
Essential to clean environment
- Eliminate spores and hyphae
- Identify and treat or remove carriers
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